(#33) - Remove portfinder package

The package did not solve the problem with ports collision.

dev/testing/environment-utils.js

@@ -1,23 +1,12 @@
 'use strict';
 
-const portfinder = require( 'portfinder' );
-
 /**
  * Contain shared functions to set the testing environment
  * properly.
  * @author Marcos Barrera del Río <elyomarcos@gmail.com>
  * @module Testing/Enviroment-utils
  */
 
-/**
- * Find an available port.
- *
- * @author Marcos Barrera del Río <elyomarcos@gmail.com>
- * @returns {Promise<Number>} Returns a promise which contains
- * an available port number.
- */
-const getFreePort = () => portfinder.getPortPromise();
-
 /**
  * Compose the baseURL for the testing environment by adding
  * the `TEST_API_HOST` to a given port.
@@ -59,7 +48,6 @@ const createTestingDatabase = () => {
 if ( process.env.NODE_ENV === 'test' ) {
 
   module.exports = {
-    getFreePort,
     getBaseURLWithPort,
     createTestingDatabase,
   };